The invention relates to a method for determining the quantity of fuel injected for an internal combustion engine in dynamic transition operation.
In dynamic transition operation, such as, for example, acceleration or overrunning, a basic quantity of fuel to be injected must be increased or reduced in relation to the conditions in the steady-state operating condition. For this purpose, a correction quantity of fuel injected is used, this being determined by first of all determining a base quantity from the load and speed. This base quantity is in each case differentiated in order thereby to evaluate the degree to which the operating condition has changed. Finally, filtering is also carried out, in order to simulate the filling of the suction pipe, the build up and decay of the wall film and to compensate disturbing influences. The differentiated base quantity is here subjected as a filter input variable to a filter characteristic which contains various filter constants. These filter constants are determined experimentally and are constant.
In road tests, it has been ascertained that correction quantities of fuel injected determined in this way are in some cases too small or too large by a multiple of their order of magnitude. Moreover, they are strongly dependent on the operating point and the method is only designed for a warm engine.
FR-A-21 63 241 discloses an electrically controlled fuel injection device for internal combustion engines, in which pulsations of the air quantity signal are smoothed out with the aid of a filter.
PCT reference WO-A-88 02 811 (corresponding to U.S. Pat. No. 4,924,835) discloses the filtering of the output signals obtained from various operating parameters; likewise in order to smooth out pulsations. The filtering inevitably results in a delay in the event of a change in the signal. In order to match the said signals to the particular situation, the filter characteristic is in both cases made dependent on parameter changes. No alteration is made to the magnitude of the signal.